The beep() and flash() routines are used to signal the terminal user. The routine beep() sounds the audible alarm on the terminal, if pos-
sible; if that is not possible, it flashes the screen (visible bell), if that is possible. The routine flash() flashes the screen, and if
that is not possible, sounds the audible signal. If neither signal is possible, nothing happens. Nearly all terminals have an audible sig-
nal (bell or beep), but only some can flash the screen.